Experimental investigation of vitreous humour motion within a human eye model

Repetto, Rodolfo; Stocchino, Alessandro; Cafferata, Chiara

doi:10.1088/0031-9155/50/19/021

Cited by 66 publications

(65 citation statements)

References 7 publications

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“…With every movement of the eyeball and especially the head, the gel accelerates and then decelerates [26], and each movement has a shearing effect on the retina at all points of adhesion, creating dynamic traction [27]. Whether the dynamic traction actually causes a retinal break depends on the strength of two opposing forces: the extent, frequency and duration of the traction on one side, and a combined power of the RPE pump, the IPM and tensile strength (physical resistance) of the retina on the other side.…”

Section: The Pathoanatomy Of the Vitreoretinal Architecture And Its Cmentioning

confidence: 99%

Rhegmatogenous Retinal Detachment: A Reappraisal of Its Pathophysiology and Treatment

2013

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This article represents a synthesis of an extensive literature review and the authors' decades-long personal experience with both scleral buckling (SB) and vitrectomy for rhegmatogenous retinal detachment (RD). Presenting a coherent understanding of the pathophysiology and treatment of RD, the authors confirm numerous findings described in earlier publications but also challenge certain long-standing dogmas. The key argument made here is that it is extremely rare for the chain of events leading to an RD to start with a retinal pathology. Rather, the initial pathology is syneresis of the vitreous, which then allows gel movement (intraocular currents). At the point of vitreoretinal adhesion, dynamic traction is exerted on the retina, which may be sufficient to tear it. If the tear is operculated and the dynamic traction overcomes the forces keeping the neuroretina and retinal pigment epithelium (RPE) together, the heretofore virtual subretinal space becomes accessible through the retinal tear. The intraocular currents allow the free (nonbound) intravitreal fluid to enter the subretinal space, and once the amount of the incoming fluid overwhelms the draining capacity of the RPE, an RD ensues. Detachment of the posterior cortical vitreous (PVD) is not a necessary prerequisite to RD development; furthermore, PVD cannot be diagnosed preoperatively with adequate certainty with current technology such as biomicroscopy, ultrasonography or optical coherence tomography. The surgeon should expect no or only partial (anomalous) PVD at the time of surgical repair in over half of eyes. The treatment's primary goal must thus be weakening (pneumatic retinopexy, SB) or eliminating (vitrectomy) this dynamic traction. If vitrectomy is employed, it must be a truly complete vitreous removal. This includes a surgically induced PVD if one is not present, close shaving at the periphery, and removing the vitreous immediately behind the lens. The vitrectomy is followed by the creation of a chorioretinal scar around the tear and aided by some form of intraocular tamponade. The main function of the tamponade is not to temporarily cover the break but to significantly reduce the intraocular currents and thus prevent fluid entry through the break until the chorioretinal adhesion will have become sufficiently strong to seal the retinal edge around the tear; postoperative positioning is therefore not as important as currently assumed.

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Section: The Pathoanatomy Of the Vitreoretinal Architecture And Its Cmentioning

confidence: 99%

Rhegmatogenous Retinal Detachment: A Reappraisal of Its Pathophysiology and Treatment

2013

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“…1989). Repetto et al (2005) propose a fifth-order polynomial to describe the time law of a saccadic movement (angle of rotation θ as function of time t), which well approximates real eye movements (see Fig. 2).…”

Section: Introductionmentioning

confidence: 99%

Traction on the retina induced by saccadic eye movements in the presence of posterior vitreous detachment

Repetto

Tatone

Testa

et al. 2010

Biomech Model Mechanobiol

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Posterior vitreous detachment is a fairly common condition in elderly people. Tractions exerted by the detached vitreous on the retina may result in retinal tears and detachments. We studied how these tractions can arise from saccadic eye movements. Numerical simulations have been performed on a two-dimensional model of the vitreous chamber within a rigid spherical sclera, subjected to prescribed finite-amplitude rotations about a vertical axis. The vitreous chamber was assumed to be split into two regions: one occupied by the detached vitreous, modeled as an elastic viscous solid, and the other occupied by the separated liquefied vitreous, modeled as a Newtonian fluid. At the interface between the two phases, we also considered the presence of the vitreous cortex, modeled as an elastic membrane. We tested several different configurations of the interface. In all cases, we found that eye rotations generate large tractions on the retina close to the attachment points of the membrane. Comparing them, we identified configurations of the vitreous detachment that exhibit higher tractions. We also investigated how the response to saccadic movements depends on some physical parameters, in particular on the rheological properties of the solid phase and the membrane. The numerical simulations show that the generated tractions may be of the same order of magnitude as the adhesive force between the retina and the pigment epithelium. Therefore, the model provides a sound physical justification for the hypothesis that saccadic movements, in the presence of posterior vitreous detachment, could be responsible for high tractions on the retina, which may trigger retinal tear formation.

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“…David et al (1998) modeled the vitreous humor as a viscoelastic fluid, and found the leading-order flow analytically in the limit of small-amplitude sinusoidal oscillations. Repetto et al (2005) used a perspex model filled with a Newtonian fluid to obtain PIV flow measurements during both idealized sinusoidal oscillations and models of real saccades. Repetto et al (2008) showed experimentally and analytically that, in addition to a leading-order oscillatory flow, a Newtonian fluid undergoing small-amplitude sinusoidal oscillations also has a steady streaming component that appears at second order and consists of two counter-rotating toroidal vortices, one in each hemisphere.…”

Section: Introductionmentioning

confidence: 99%

Mathematical model of flow in the vitreous humor induced by saccadic eye rotations: effect of geometry

Repetto

Siggers

Stocchino

2009

Biomech Model Mechanobiol

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Saccadic eye rotations induce a flow in the vitreous humor of the eye. Any such flow is likely to have a significant influence on the dispersion of drugs injected into the vitreous chamber. The shape of this chamber deviates from a perfect sphere by up to 10-20% of the radius, which is predominantly due to an indentation caused by the lens. In this paper we investigate theoretically the effect of the domain shape upon the flow field generated by saccades by considering an idealized model. The posterior chamber geometry is assumed to be a sphere with a small indentation, undergoing prescribed small-amplitude sinusoidal torsional oscillations, and, as an initial step towards understanding the problem, we treat the vitreous humor as a Newtonian fluid filling the chamber. The latter assumption applies best in the case of a liquefied vitreous or a tamponade fluid introduced in the vitreous chamber after vitrectomy. We find the flow field in terms of vector spherical harmonics, focusing on the deviation from the flow that would be obtained in a perfect sphere. The flow induced by the departure of the domain geometry from the spherical shape has an oscillating component at leading order and a smaller-amplitude steady streaming flow. The oscillating component includes a circulation cell formed every half-period, which migrates from the indentation towards the center of the domain where it disappears. The steady component has two counter-rotating circulations in the anterior part of the domain. These findings are in good qualitative agreement with the experimental results of Stocchino et al. (Phys Med Biol 52:2021-2034, 2007). Our results predict a significant reduction in the expected time for drug dispersal across the eye compared with the situation in which there is no fluid flow present.

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Experimental investigation of vitreous humour motion within a human eye model

Cited by 66 publications

References 7 publications

Rhegmatogenous Retinal Detachment: A Reappraisal of Its Pathophysiology and Treatment

Rhegmatogenous Retinal Detachment: A Reappraisal of Its Pathophysiology and Treatment

Traction on the retina induced by saccadic eye movements in the presence of posterior vitreous detachment

Mathematical model of flow in the vitreous humor induced by saccadic eye rotations: effect of geometry

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